ICE3AS02 datasheet(9/23 Pages) INFINEON

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ICE3AS02 / ICE3AS02G / ICE3BS02 / ICE3BS02G

Functional Description

Version 1.1

21 May 2004

Once the malfunction condition is removed, this block

will then turn back on. The recovery from Auto Restart

Mode does not require disconnecting the SMPS from

the AC line.

When Active Burst Mode is entered, the internal Bias is

switched off in order to reduce the current consumption

to below 1.05mA while keeping the Voltage Reference

active as this is necessary in this mode.

3.3

Startup Phase

Figure 5

Soft Start

At the beginning of the Startup Phase, the IC provides

a Soft Start duration whereby it controls the maximum

primary current by means of a duty cycle limitation. A

signal V

SoftS

which is generated by the external

capacitor C

Softs in combination with the internal pull up

resistor R

SoftS, determines the duty cycle until VSoftS

exceeds 4V.

When the Soft Start begins, C

SoftS

is immediately

charged up to approx. 1V by T2. Therefore the Soft

Start Phase takes place between 1V and 4V. Above

SoftsS = 4V there is no longer duty cycle limitation

max which is controlled by comparator C7 since

comparator C2 blocks the gate G7 (see Figure 5). The

maximum charge current in the very first stage when

SoftS is below 1V, is limited to 1.32mA.

Figure 6

Startup Phase

By means of this extra charge stage, there is no delay

in the beginning of the Startup Phase when there is still

no switching. Furthermore Soft Start is finished at 4V to

have faster the maximum power capability. The duty

cycles DC

1 and DC2 are depending on the mains and

the primary inductance of the transformer. The

limitation of the primary current by DC

2 is related to

SoftS = 4V. But DC1 is related to a maximum primary

current which is limited by the internal Current Limiting

with CS = 1V. Therefore the maximum Startup Phase

is divided into a Soft Start Phase until t1 and a phase

from t1 until t2 where maximum power is provided if

demanded by the FB signal.

Soft-Start

Comparator

Soft Start

SoftS

3.25k

6.5V

SoftS

Gate Driver

0.85V

x3.7

PWMOP

max

SoftS

max. Soft Start Phase

5.4V

max. StartupPhase

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